题目描述
We arrange the numbers between 1 and N (1 <= N <= 10000) in increasing order and decreasing order like this:
1 2 3 4 5 6 7 8 9 . . . N
N . . . 9 8 7 6 5 4 3 2 1
Two numbers faced each other form a pair. Your task is to compute the number of pairs P such that both numbers in the pairs are prime.
Input
Input contains several test cases. Each test case consists of an integer N in one line.
Output
For each line of input, output P .
Example
Input
1
4
7
51
Output
0
2
2
6
输入格式
见题面
输出格式
见题面
样例输入
1
4
7
51
样例输出
0
2
2
6